如何将对象从 React Native Android 模块传递回 Javascript

Question

React Native's Native Module documentation for Android says that ReadableMap directly maps to a Javascript object. I assume this means that when I pass an object from Javascript to a native module, it is available as a ReadableMap .

How do I do the reverse, which is to create a dictionary (mapping string to string) in a native module and return it to Javascript via a callback ?

Answer 1

You can use WritableMap to simply pass map values through callback.

@ReactMethod
public void pass(Callback cb) {
    HashMap<String, String> hm = new HashMap<>();
    hm.put("A", "one");
    hm.put("B", "Two");
    hm.put("C", "Three");
    WritableMap map = new WritableNativeMap();
    for (Map.Entry<String, String> entry : hm.entrySet()) {
        map.putString(entry.getKey(), entry.getValue());
    }
    cb.invoke(map);
}

for more complex data, see this blog .

Answer 2

For React Native >=0.62 , you can use this:

import com.facebook.react.bridge.WritableMap;
import com.facebook.react.bridge.Arguments;

@ReactMethod
public void test(Callback callback) {
    WritableMap map = Arguments.createMap();

    map.putString("yourKey", "yourValue");

    callback.invoke(map);
}

To call the native function in React Native, do this:

import { NativeModules } from 'react-native';

NativeModules["replaceWithTheModuleName"].test(res => {
  console.log(res);
})